The present invention broadly relates to an apparatus for mutually positioning roll surfaces of rolls in a roll calender and, more specifically pertains to a new and improved apparatus for neutralizing overhanging or cantilever loads at rolls of a roll calender which is to be downwardly opened.
Generally speaking, the apparatus of the present invention is of the type which is supported at a roll stand of the roll calender, provided at both sides of the rolls or rollers and in each case presses against a related roll suspension in a predetermined or required position of the related roll or roller with a force which compensates for the overhanging or cantilever loads.
A calender which is known to the art comprises a number of intermediate rolls or rollers which are arranged between an uppermost roll or roller and a lowermost roll or roller. During operation, these intermediate rolls or rollers of the calender are pressed against one another by raising the lowermost roll or roller. The calender is opened by lowering the lowermost roll or roller and the intermediate rolls or rollers are lowered by their own weight into predetermined or desired spatial positions, the intermediate rolls or rollers assuming or retaining a defined spacing from one another. This lowering must be very rapidly accomplished, for example, in the event of an operational disturbance or breakdown. The working or operating pressure in the individual nips between the intermediate rolls or rollers results from the sum of the forces with which the individual intermediate rolls or rollers act from above and in the downward direction upon the respective lower roll or roller. In addition thereto, the so-called overhanging or cantilever loads deformingly act upon the axles or journals of the intermediate rolls or rollers. In this regard there is to be understood in terms of such loads all of the weight of the roll portions or sections on both sides of the material web to be treated, the weight of the journals of the rolls or rollers and of the bearings thereof, the weight of guide rollers possibly suspended thereat and the weight of finger protector devices and the like. These weights can amount at each side to 15 kN and more. The deforming action of such overhanging or cantilever loads is substantially prevented in that such overhanging or cantilever loads are counteracted by a corresponding force.
For this purpose, there are known support structures, in most cases hydraulic piston-and-cylinder units, by means of which the aforesaid corresponding force is set and retained. During the so-called "opening" or nip relieving of the roll calender, the hydraulic or pressurized fluid medium located in the cylinder must be expelled by means of a switching or control operation. The lowering displacement path of the intermediate rolls or rollers into the lowered position can be determined or given by the quantity of expressed or expelled hydraulic or pressurized fluid medium. However, a limit stop or impact member can also serve as a displacement path limitation facility.
These known support structures or units perform satisfactorily and are reliable in operation, but they are complicated in construction and design and thus require a corresponding expenditure for the hydraulic piston-and-cylinder units and the control engineering circuits particularly required to control the chronological sequence of the individual lowering of the intermediate rolls or rollers.